Engineering Physics Questions and Answers – Gases and Reactions

This set of Engineering Physics Multiple Choice Questions & Answers (MCQs) focuses on “Gases and Reactions”.

1. In a vessel, the gas at a pressure P. If the mass of all molecules is halved and their speed is doubled, then the resultant pressure will be ___________
a) 4P
b) 2P
c) P
d) P/2
View Answer

Answer: c
Explanation: According to the kinetic theory of gases, the pressure exerted by a gas,
P=1/3×mn/V v2
P/P=2
P=2P.

2. The absolute zero is the temperature, at which?
a) All substances exist in a solid state
b) Water freezes
c) Molecular motion ceases
d) Solid melts
View Answer

Answer: c
Explanation: The absolute zero is the temperature at which all molecular motion ceases.

3. When we heat a gas-sample from 27°C to 327°C, then the initial average kinetic energy of the molecules was E. What will b the average kinetic energy?
a) 327E
b) 300E
c) 2E
d) √2E
View Answer

Answer: c
Explanation: E/E=(273+327)/(273+27)=600/300
E=2E.
advertisement

4. Temperature less than absolute zero is not possible.
a) True
b) False
View Answer

Answer: a
Explanation: According to the kinetic interpretation of temperature, absolute temperature is proportional to the average kinetic energy of molecules. As the heat is removed, the temperature falls and velocity of molecules decreases. At absolute zero, the kinetic energy becomes zero. As the kinetic energy cannot be negative so no further decrease in kinetic energy is possible. Hence temperature cannot be decreased below absolute zero.

5. A given quantity of an ideal gas at pressure P and absolute temperature T. The isothermal bulk modulus of the gas is ___________
a) 2/3 P
b) P
c) 3/2 P
d) 2P
View Answer

Answer: a
Explanation: At a given temperature,
P∆V+V∆P=0
P=V∆P/∆V=(∆P/∆V)/V=Isothermal bulk modulus.
Free 30-Day Python Certification Bootcamp is Live. Join Now!

6. Statement: The ration Cp/Cv is more for helium gas than that for hydrogen gas.
Reason: Atomic mass of helium is more than that of hydrogen.
a) Both statement and reason are true and the reason is the correct explanation of the statement
b) Both statement and reason are true but the reason is not a correct explanation of the statement
c) Statement it true but the reason is false
d) Both statement and reason are false
View Answer

Answer: a
Explanation: Both the statement and reason are true but the reason is not a correct explanation of the statement
For monoatomic He,
γ=Cp/Cv = 5/3
For diatomic H2,
γ=Cp/Cv = 7/5.

7. The relation PV=RT can describe behaviour of the real gas at ___________
a) High temperature and high density
b) High temperature and low density
c) Low temperature and low density
d) Low temperature and high density
View Answer

Answer: b
Explanation: At high temperature and low density, real gas behaves like an ideal gas. Then the intermolecular attractions and actual volume of gas molecules become negligible.

8. An absolute zero is the temperature at which?
a) Water solidifies
b) All gases become liquid
c) rms velocity becomes zero
d) Solids melt
View Answer

Answer: c
Explanation: According to the kinetic theory of gases, absolute zero is that temperature at which all molecular motion ceases. Hence at T=0K, rms velocity becomes zero.

9. The temperature of a given mass is increased from 27°C to 327°C. The rms velocity of the molecules increases ___________
a) √2 times
b) 2 times
c) 2√2 times
d) 4 times
View Answer

Answer: a
Explanation: vrms is proportional √T
v2/v1 =√(T2/T1)=√((273+327)/(273+27))=√(600/300)=√2
v2=√2 v1.
advertisement

10. The ratio of the vapour densities of two gases at a given temperature is 9:8. The ratio of the rms velocities of their molecules is ___________
a) 3:2√2
b) 2√2:3
c) 9:8
d) 8:9
View Answer

Answer: b
Explanation: At a given temperature,
(vrms (1))/(vrms (2))=√(8/9)=2√2:3.

Sanfoundry Global Education & Learning Series – Engineering Physics.

To practice all areas of Engineering Physics, here is complete set of 1000+ Multiple Choice Questions and Answers.

advertisement
advertisement
Subscribe to our Newsletters (Subject-wise). Participate in the Sanfoundry Certification contest to get free Certificate of Merit. Join our social networks below and stay updated with latest contests, videos, internships and jobs!

Youtube | Telegram | LinkedIn | Instagram | Facebook | Twitter | Pinterest
Manish Bhojasia - Founder & CTO at Sanfoundry
I’m Manish - Founder and CTO at Sanfoundry. I’ve been working in tech for over 25 years, with deep focus on Linux kernel, SAN technologies, Advanced C, Full Stack and Scalable website designs.

You can connect with me on LinkedIn, watch my Youtube Masterclasses, or join my Telegram tech discussions.

If you’re in your 40s–60s and exploring new directions in your career, I also offer mentoring. Learn more here.